1. Field of Invention
The present invention relates to a time adjustment device that adjusts the time based on time information contained in signals transmitted from the base station of a CDMA (Code Division Multiplex Access) cell phone network, for example. The invention also relates to a timepiece having the time adjustment device, and to a time adjustment method.
2. Description of Related Art
Time information is contained in signals transmitted to cell phones from the base stations in modern CDMA cell phone networks. This time information is extremely precise time information that matches the GPS time, which is based on the atomic clocks on GPS (Global Positioning System) satellites.
Japanese Unexamined Patent Appl. Pub. JP-A-2000-321383 (see the abstract) teaches a terminal that acquires the GPS time data transmitted from a base station of a CDMA cell phone network, and uses the GPS time data to correct the time kept by an internal clock.
CDMA cell phone networks are, however, operated by multiple different cell phone service providers. The reliability of the time information in signals transmitted from the base stations of these cell phone service providers may therefore differ according to the cell phone service provider.
Therefore, in order to ensure that a time adjustment device can accurately adjust the time based on the time information received from the base station, the circuit design and parameters, for example, of the time adjustment device must match the particular cell phone service provider, thus increasing the production cost.